CEOs and their finance chiefs are in a tight spot this month as they report quarterly financial data, aiming for a delicate balance of realism and optimism.

Among the things having as good a decade as the U.S. economy is Apple’s iPhone. Rummage through the pockets and purses of your workmates, and chances are you’ll find one.

The health of the near-ubiquitous smartphone and the economic engine it has helped drive and ride are both under a growing cloud, though. Apple Inc. slashed its revenue target this week as iPhone sales slumped, a development that tests the nerves of investors already on the lookout for signs of the first American economic downturn since 2009.